1. Field of the Invention
The present invention relates to a method of and an apparatus for continuously cutting fibers and, particularly, those known as super high-tenacity fibers, to a predetermined length.
2. Description of the Prior Art
Various methods of and/or apparatus suitable for cutting particular types of fibers have hitherto been suggested. As is well known to those skilled in the art, of inorganic fibers including steel fibers, glass fibers, ceramics fibers and carbon fibers, the glass fibers, the ceramics fibers and the carbon fibers have long been recognized as having both a relatively high tensile strength and a relatively high rigidity, but being relatively fragile. Because of those properties, the cutting of the glass fibers, the ceramics fibers or the carbon fibers is generally carried out by the use of a so-called roving cutter assembly operable to flaw the filaments or rovings by means of a plurality of metal blades. The roving cutter assembly is of a type comprising a rotatably supported cutter roller, on which the metal blades are spacedly mounted, and a counter roller cooperable with the rotary cutter roller so that, during the passage of the filaments or rovings through a nipping region defined between the cutter and counter rollers, the filaments or rovings can be cut to a predetermined or desired length.
On the other hand, when it comes to the cutting of organic synthetic fibers such as fibers of polyester, polyacryronitrile, polypropylene, polyethylene, polyvinylidene chloride, polyvinyl chloride, polyamide or polyvinyl alcohol resin, or chemical fibers such as Rayon or acetate, it is a general practice to cut these fibers by the use of a guillotine cutter after these fibers have been gathered together into a tow or a bundle of rovings or filaments, which tow or bundle has a thickness greater than some ten thousand deniers. The guillotine cutter referred to above is of a type comprising a pair of spaced apart guide rails, a stationary blade at one ends of the guide rails and a movable blade movable along the guide rails towards the stationary blade and is designed so as to cut the fibers by a scissor action.
A recent version of cutter is of a type manufactured and sold by Teijin Seiki Co., Ltd. of Japan under a tradename of "EC Cutter". This type of cutter comprises a plurality of blades arranged in a generally cylindrical configuration and is so designed that the fibers can be cut into staple fibers as the fibers are firmly wrapped around the cylinder of the blades, which staple fibers are in turn drawn inside the cylinder of the blades through a space between each neighboring blades for the discharge thereof to a collecting box or a next succeeding work station.
However, recently developed reinforcement fibers suited as a reinforcement material to be used in a composite material such as fiber reinforced plastics (FRP) or fiber reinforced thermoplastics (FRTP), which are generally referred to advanced composites material (ACM), are required to have a tensile strength not lower than 100 kg/mm.sup.2 and a modulus of elasticity not lower than 3,000 kg/mm.sup.2 but have a small thickness (fiber diameter) within the range of 5 to 50 .mu.m.
These ACM fibers are, after having been cut to a desired or required length, mixed into the composite material as reinforcement fibers. While the glass fibers are a representative of the various types of fibers which are mixed into the fiber reinforced plastics, the glass fibers are extremely fragile and often constitute a source of an environment pollution. Because of this, a recent trend is to use, in place of the glass fibers, commercially available super high-tenacity fibers such as fibers of polyvinyl alcohol sold under a tradename "TAFTEC" (manufactured and sold by Kuraray Co., Ltd. of Japan), fibers of all aromatic polyamido sold under a tradename "Kevlar" (manufactured and sold by E.I. Du Pont de Nemours and Company) or "TECHNORA" (manufactured and sold by Teijin Limited of Japan), fibers of all aromatic polyester sold under a tradename "VECTORAN" (manufactured and sold by Kuraray Co., Ltd. of Japan), or fibers of polyethylene sold under a tradename "Dyneema" (manufactured and sold by Toyobo Co., Ltd. of Japan). However, it has been found that, since these super high-tenacity fibers are extremely slender, flexible and rigid, the conventional cutting method can hardly be employed to cut these super high-tenacity fibers continuously at a high speed.
More specifically, when an attempt is made to cut the super high-tenacity fibers continuously by the use of the conventional roving cutter, the cutting blade is susceptible to a reduction in sharpness to such an extent that the satisfactory cutting cannot be attained even though the force necessary to cut is increased and, in the extreme case it may happen, the cutting will no longer be accomplished. On the other hand, if the use of the conventional guillotine cutter, which is generally considered effective for cutting a fiber tow of a thickness greater than some ten thousands deniers, is used to cut the super high-tenacity fiber continuously, not only is the cutting blade readily susceptible to a reduction in sharpness, but the blade edge thereof tends to be spoiled and/or a zone of heat fusion occurs at a cutting region, failing to properly cut the super high-tenacity fiber.
The conventional guillotine cutter is based on the principle that the cutting blade should have a sharp blade edge to cut a material to be cut. Accordingly, when it comes to the cutting of the super high-tenacity fiber of such a property as hereinbefore described with the use of the guillotine cutter, it appears that a satisfactory cutting cannot be accomplished, resulting an improper cutting of the fiber. In the case where the super high-tenacity fiber is to be cut with the use of the EC cutter which has a cutting mechanism substantially similar to that exhibited by the guillotine cutter, the super high-tenacity fiber tends to be tightened as a result of an increase of the fiber turning force in proportion to the reduction in sharpness of the cutting blade and, therefore, the cutting blade is susceptible to a breakage, failing to accomplish a smooth and proper cutting.